1. Field of the Invention
The present invention relates to a toner conveying device that conveys toner from a toner container to a developing device in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or other similar image forming apparatus.
2. Discussion of the Background
An image forming apparatus such as a copying machine, a facsimile machine, a printer, or other similar image forming apparatus that forms images by use of a powder-shaped developer, such as toner, and a two-component developer including toner and magnetic carrier, has been widely used. In an electrophotographic image forming apparatus, a toner image is generally formed by developing an electrophotographic latent image formed on a latent image carrier with toner by a developing device. In the above-described image forming apparatus, it is necessary to supply toner to a developing device at an appropriate timing as image forming operations are repeated. To supply toner to a developing device, for example, an image forming apparatus includes a toner conveying device that urges the discharge of toner from a toner container, such as a toner bottle and a toner cartridge, by vibrating the toner container and that conveys the toner discharged from the toner container to a developing device through a toner conveying tube.
In the image forming apparatus including such a toner conveying device, an amount of toner supplied from a toner container to a developing device tends to be unstable depending on the condition of the toner in the toner container. Specifically, toner tends to be not easily discharged from the toner container due to the agglomeration of toner and the decrease of fluidity of toner caused by the moisture absorption of the toner. Therefore, the amount of toner supplied from a toner container to a developing device typically decreases in a relatively high humidity environment. When the amount of toner supplied from the toner container to the developing device becomes unstable, image quality deteriorates.
Further, in an image forming apparatus including a toner conveying device, when all the toner in the toner container is consumed, the toner container is replaced with a new one. If a large amount of toner remains in a used toner container when replacing the used toner container, the remaining toner is unnecessarily disposed of, thereby increasing the operating expense of the image forming apparatus, and harming the environment. For these reasons, it is desirable that the remaining amount of toner in the toner container should be monitored by a sensor, and the timing of replacement of the toner container should be adequately judged. However, if a sensor is provided in a disposable toner container, the cost of the toner container increases.
The above-described problems may occur not only in a toner conveying device in an image forming apparatus that conveys toner from a toner container to a developing device, but also in any types of powder conveying device that conveys powder from a powder container to a desired device.
Recently, electrophotographic image forming apparatuses have been downsized, and demands for a multi-color image forming apparatus have increased. Accordingly, each unit in an image forming apparatus needs to be downsized, and therefore the size of a developing device is decreased, so that toner needs to be frequently supplied from a toner container to the developing device.
When a toner end condition, in which the amount of the toner in a toner container is low or nearly nil, is not detected, a user finds the toner end condition just by seeing a deteriorated image. To avoid this problem, a detecting mechanism needs to be provided to detect the presence or absence of toner in a toner container.
For example, a background image forming apparatus includes a remaining toner amount detecting device, and a toner removing device that removes toner adhered to the remaining toner amount detecting device. When detecting the presence or absence of toner in a toner container by a remaining toner amount detecting device, the detection surface of the remaining toner amount detecting device needs to avoid forming a toner stain to avoid a detection error. Generally, the detection surface of a remaining toner amount detecting device is formed from a resin material in view of cost and process.
For example, one method of avoiding a detection error is a toner removing device that removes toner adhered to the detection surface of the remaining toner amount detecting device. In another method, a detection surface or a detecting device is provided to a toner container which is replaced after a relatively short period. In this case, even if toner is adhered to the detection surface, the detection surface is renewed by replacing the toner container.
However, in the former method, in addition to a toner removing device, a drive device that drives the toner removing device needs to be provided, thereby increasing the cost of the apparatus. Further, the location of the toner removing device is limited in an image forming apparatus. In the latter method, a detection error may be caused when a greater than expected amount of toner is adhered to the detection surface of the detecting device. Further, the latter method cannot be applied to a toner container which is replaced after a relatively long period.
Therefore, it is desirable to provide an image forming apparatus including a toner conveying device that can stabilize the amount of toner conveyed and can notify the user of the need for adequate replacement of a toner container. Further, the apparatus should be of simple construction and without increased expense. Further, it is desirable to provide an image forming apparatus including a toner conveying device having a detection device that can adequately detect the presence or absence of toner in a toner container over a long time period while preventing the adhesion of toner to the detection surface of the detection device without cleaning the detection surface of the detecting device.